And of course, if I did this no one would give me an absolute penny. But you see, it's already being done for us. Those experiments have been done, we've got the mutants, we've got the human mutants and we still have some representative of the original stock, the fish. Therefore, why don't we just do genetics on these? So why don't I just do the following, I'll take a gene out of the fish and put it into a man. Well, can't do that, so I'll do it in a mouse, which is the experimental animal. And now I'll ask for that gene, do you work in the mouse? Now, the mouse, of course, could be argued from point of view of physiology and anatomy to have a fishy part and to have something that got added on. There still is a fishy part to the mouse. The immunology will still be fishy; no, but the lungs certainly won't be, because they just aren't present in this. So if I find this gene, let us say, that expresses in the lungs of a human and I find the same gene in a fish, I can ask whether that fish gene will express in the lungs. Now, if it doesn't – so this only will express in the fishy part of the mouse – I have to say that that gene just retains that information, all right, and therefore I should look at the mouse gene there to see what has happened here. Has other things been added on? Has it moved to another place, perhaps, where it has a different regulation? That's probably what would have happened. Then in the other case, if the fishy gene expresses all over the mouse, that is you couldn't tell the difference between the two mice, one with a mouse gene and one with a fish gene, then I have the right to say that evolution went at a higher level in the program and this remained the same. So what we can find throughout these is those invariant parts of the genome that just stayed the same and which we expect will be… will be invariant in the sense that as we all know, in development, when you want a new muscle you don't start from the beginning again and reinvent all the proteins, you just have a way of saying: do what you know, but do it here and not there. So I think that this is the way really to do the genetics of complex regulation. And I think the present idea of doing it by cutting out a piece and seeing what happens, this is… this is going to be just too tedious and too boring to do.

South African Sydney Brenner (1927-2019) was awarded the Nobel Prize in Physiology or Medicine in 2002. His joint discovery of messenger RNA, and, in more recent years, his development of gene cloning, sequencing and manipulation techniques along with his work for the Human Genome Project have led to his standing as a pioneer in the field of genetics and molecular biology.

Lewis Wolpert is Professor of Biology as Applied to Medicine in the Department of Anatomy and Developmental Biology of University College, London. His research interests are in the mechanisms involved in the development of the embryo. He was originally trained as a civil engineer in South Africa but changed to research in cell biology at King's College, London in 1955. He was made a Fellow of the Royal Society in 1980 and awarded the CBE in 1990. He was made a Fellow of the Royal Society of Literature in 1999. He has presented science on both radio and TV and for five years was Chairman of the Committee for the Public Understanding of Science.